An appraisal of the role of specific bacteria in the initial pathogenesis of periodontitis

Background Historically, inflammatory periodontal diseases (gingivitis and periodontitis) have been recognized as being primarily of bacterial origin. Bacteria are necessary for disease development, but the presence of specific bacteria does not guarantee progression to periodontitis. Periodontitis is a multifactorial disease; specific bacteria are associated with disease, but may not be the target of treatment. Gingivitis and periodontitis are inflammatory conditions associated with bacterial overgrowth. Aim To analyse evidence for established thought that specific bacteria directly participate in the pathogenesis of periodontitis and question the long-held tenet that penetration of the periodontal connective tissues by bacteria and their products is a significant phase in the initial development of periodontitis. Methods The literature was searched for studies on initiation of gingivitis and periodontitis by specific pathogens. The search results were insufficient for a systematic review and have been summarized in a commentary instead. Results There is very little evidence in the literature to support the commonly held concept that specific bacteria initiate periodontitis. Conclusion We present evidence for a paradigm supporting the central role of inflammation, rather than specific microbiota, in the early pathogenesis of periodontitis, and discuss whether controlling the inflammation can influence the character and composition of the periodontal infection.